1. Field of the Invention
This invention relates to orthodontic headgear of the J-hook type for transmitting extraoral force from such headgear by the J-hook to intraoral orthodontic apparatus, which force can be adjusted to different degrees and which J-hook is disconnectible automatically from the headgear if a force exceeding a predetermined force is exerted on it.
2. Prior Art
The headgear of the present invention is of the general type shown in FIGS. 5 and 6 of Armstrong U.S. Pat. No. 3,526,035, issued Sept. 1, 1970, which headgear is stated at column 5, line 61 to column 6, line 3, to have a wire-coupling member 71 that includes an inwardly curved portion 77 terminating in an eye 78 that can be connected to an intraoral orthodontic appliance. This general type of orthodontic appliance has become known commonly as a "J-hook type" and that terminology is used in the present specification.
Orthodontic headgear of the force-adjustable type and having a connector which is disconnectible automatically if a force exceeding a predetermined force is exerted on it is disclosed in Armstrong et al. U.S. Pat. No. 4,553,933, issued Nov. 19, 1985. In the headgear of that patent, however, a headcap is connected to a facebow by side straps rather than J-hooks being used as in the present invention.